OSPF Frame-Relay problem

[chrisayres]

OK

I have got a hub and spoke frame relay setup. No sub ints just "enc frame-relay" on the physical ints. I have all ints in the same subnet I have setup all the frame-relay maps and can ping everything from everything else.

I have setup ospf with all relevant neigbour statements. OSPF is OK between the hub and all the spokes, but I cant get ospf to form adj's between the spokes. What am I doing wrong

[Richard Burts]

Chris

Since the spokes can not send multicast to each other (since they are not directly connected) they can not form adjacencies. That is one of the reasons that it is important that the hub router be the DR for that subnet. Each spoke becomes adjacent with the hub, the hub knows the topology information from each spoke, and the hub will advertise the topology information of each spoke to the other spokes. But the spokes will not be adjacent with each other. One of the advantages of point to point subinterfaces is that you avoid the ambiguity of which routers are adjacent neighbors and which are not. Also with point to point subinterfaces there is no dependency on the hub router being the DR.

HTH

Rick

[chrisayres]

Hi,

I thought the point of the neighbor statment in OSPF was to force the router to unicast rather than multicast, if this is the case if a ping works why doesn't OSPF. i have put a ip pac debug on and then configured the neighbor, when I do this I do see a unicast packet going to the neighbor I just defined (ie the other spoke) but i don't see this arrive at the other router.

I am only playing in the lab trying to get a better understanding of OSPF and FR

[sundar.palaniappan · Accepted solution]

Chris,

Your understanding of neighbor statement is correct as it would cause the router to send unicast hellos instead of multicast packets. However, in your setup, the hub router would still have to route the OSPF hello packets to the other spokes as there's no direct connection (PVC) between the spokes. Hellos have a TTL of 1 and cannot be routed.

As Rick had stated in his earlier post, you need to configure your hub to be the DR and the spokes would form neighbor relationship only with the hub. All traffic from or between the spokes would all be routed through the hub. Your other option is to have a full mesh NBMA setup and that is expensive and uncommon setup.

HTH

Sundar

[chrisayres]

Sundar, Rick

Thanks for your answers, I have got ospf and FR working as you suggested. As I said I was only playing around in the lab to see what I could get it to do (or not do)

Thanks again